A prospective study evaluating the functionality and ease of use of the Medtronic CareLink Network, "CareLink," was conducted at ten investigational sites. This internet-based remote monitoring service allows clinicians to remotely manage their patients' implantable cardioverter defibrillators (ICDs) and chronic diseases. The network is comprised of a patient monitor, a secure server, and clinician and patient websites. Under clinician direction, patients interrogated their ICDs at home, and transmitted data to secure servers via a standard telephone line. Comprehensive device data and a 10-second presenting rhythm electrogram were captured by the monitor and available for access and review on the clinician website. The information could also be printed using a standard desktop computer with internet access. During this study, patients were asked to transmit device data twice, at least 7 days apart, as scheduled by the clinic. Monitor functionality was assessed, and ease of using the system components was evaluated via questionnaires completed by patients and clinicians following each data transmission and review. Fifty-nine patients (64 +/- 14 years, range 22-85 years) completed 119 transmissions with only 14 calls to the study support center. Clinician review of data transmissions revealed several clinically significant findings, including silent AF discovery, assessment of antiarrhythmic drug efficacy in a previously diagnosed AF patient, previously unobserved atrial undersensing, and ventricular tachycardia. ICD patients found the monitor easy to use. Clinicians were pleased with the performance of the network and the quality of the web-accessed data, and found it comparable to an in-office device interrogation. CareLink is a practical tool for routine device management and may allow timely identification of clinically important issues.